As expected, the lowest proportion of breast cancer specific deaths was noted in those with grade-1 tumours [2.4%; 10-year-survival = 95.5% (95% CI 70.7–99.3)] and CIS [2.8%; 10-year-survival = 98.2% (95% CI 87.6–99.7)], although breast cancer specific survival was also excellent in grade-2 ER + HER2- breast cancer [10-year-survival = 95.1% (95% CI 85.3–98.4)]. This evidence concerns the gene ERBB2 and breast cancer.